ArrayMesh.cpp

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/* *****************************************************************
    MESQUITE -- The Mesh Quality Improvement Toolkit

    Copyright 2007 Sandia National Laboratories.  Developed at the
    University of Wisconsin--Madison under SNL contract number
    624796.  The U.S. Government and the University of Wisconsin
    retain certain rights to this software.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    (lgpl.txt) along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    (2007) kraftche@cae.wisc.edu

  ***************************************************************** */

/** \file ArrayMesh.cpp
 *  \brief
 *  \author Jason Kraftcheck
 */

#include "Mesquite.hpp"
#include "ArrayMesh.hpp"
#include "TopologyInfo.hpp"
#include "MsqError.hpp"
#include "MsqVertex.hpp"

#include <iostream>

namespace MBMesquite
{

class IndexIterator : public EntityIterator
{
  public:
    IndexIterator( size_t pStart, size_t pEnd ) : mStart( pStart ), mEnd( pEnd ), mCurrent( pStart ) {}
    virtual ~IndexIterator() {}
    virtual void restart()
    {
        mCurrent = mStart;
    }
    virtual Mesh::EntityHandle operator*() const
    {
        return (Mesh::EntityHandle)mCurrent;
    }
    virtual void operator++()
    {
        ++mCurrent;
    }
    virtual bool is_at_end() const
    {
        return mEnd - mCurrent <= 1;
    }

  private:
    size_t mStart, mEnd, mCurrent;
};

ArrayMesh::ArrayMesh()
    : mDimension( 0 ), vertexCount( 0 ), coordArray( 0 ), fixedFlags( 0 ), slavedFlags( 0 ), vertexByteArray( 0 ),
      elementCount( 0 ), connArray( 0 ), connOffsets( 0 ), allocConnOffsets( 0 ), elementType( MIXED ),
      elementTypes( 0 ), nodesPerElement( 0 ), oneBasedArrays( false ), vertexAdjacencyList( 0 ),
      vertexAdjacencyOffsets( 0 ), tagList( 0 )
{
}

ArrayMesh::ArrayMesh( int coords_per_vertex,
                      unsigned long num_vertices,
                      double* interleaved_vertex_coords,
                      const int* vertex_fixed_flags,
                      unsigned long num_elements,
                      EntityTopology element_type,
                      const unsigned long* element_connectivity_array,
                      bool one_based_conn_indices,
                      unsigned nodes_per_element,
                      const int* vertex_slaved_flags )
    : mDimension( coords_per_vertex ), vertexCount( num_vertices ), coordArray( interleaved_vertex_coords ),
      fixedFlags( vertex_fixed_flags ), slavedFlags( vertex_slaved_flags ),
      vertexByteArray( new unsigned char[num_vertices + one_based_conn_indices] ), elementCount( num_elements ),
      connArray( element_connectivity_array ), connOffsets( 0 ), allocConnOffsets( 0 ), elementType( element_type ),
      elementTypes( 0 ), nodesPerElement( nodes_per_element ), oneBasedArrays( one_based_conn_indices ),
      vertexAdjacencyList( 0 ), vertexAdjacencyOffsets( 0 ), tagList( 0 )
{
    if( oneBasedArrays )
    {
        coordArray -= mDimension;
        --fixedFlags;
    }

    if( nodesPerElement < 2 ) nodesPerElement = TopologyInfo::corners( element_type );

    assert( valid() );
    memset( vertexByteArray, 0, num_vertices + one_based_conn_indices );
}

ArrayMesh::ArrayMesh( int coords_per_vertex,
                      unsigned long num_vertices,
                      double* interleaved_vertex_coords,
                      const int* vertex_fixed_flags,
                      unsigned long num_elements,
                      const EntityTopology* element_types,
                      const unsigned long* element_connectivity_array,
                      const unsigned long* element_connectivity_offsets,
                      bool one_based_conn_indices,
                      const int* vertex_slaved_flags )
    : mDimension( coords_per_vertex ), vertexCount( num_vertices ), coordArray( interleaved_vertex_coords ),
      fixedFlags( vertex_fixed_flags ), slavedFlags( vertex_slaved_flags ),
      vertexByteArray( new unsigned char[num_vertices + one_based_conn_indices] ), elementCount( num_elements ),
      connArray( element_connectivity_array ), connOffsets( element_connectivity_offsets ), allocConnOffsets( 0 ),
      elementType( MIXED ), elementTypes( element_types ), nodesPerElement( 0 ),
      oneBasedArrays( one_based_conn_indices ), vertexAdjacencyList( 0 ), vertexAdjacencyOffsets( 0 ), tagList( 0 )
{
    if( oneBasedArrays )
    {
        coordArray -= mDimension;
        --fixedFlags;
        if( element_connectivity_offsets ) --connArray;
    }

    if( !element_connectivity_offsets )
    {
        connOffsets = allocConnOffsets = new unsigned long[num_elements + 1];
        allocConnOffsets[0]            = 0;
        for( unsigned long i = 1; i <= num_elements; ++i )
            allocConnOffsets[i] = allocConnOffsets[i - 1] + TopologyInfo::corners( elementTypes[i - 1] );
    }

    assert( valid() );
    memset( vertexByteArray, 0, num_vertices + one_based_conn_indices );
}

bool ArrayMesh::valid() const
{
    unsigned long off = oneBasedArrays ? 1 : 0;
    for( unsigned long i = off; i < vertexCount + off; ++i )
    {
        if( fixedFlags[i] != 0 && fixedFlags[i] != 1 )
        {
            std::cerr << "Invalid vertex fixed flag at index " << i << std::endl;
            return false;
        }
    }

    for( unsigned long i = 0; i < elementCount * nodesPerElement; ++i )
    {
        unsigned long j = connArray[i] - oneBasedArrays;
        if( j >= vertexCount )
        {
            std::cerr << "Invalid connectivity index at index " << j << "(element " << j / elementCount << " node "
                      << j % elementCount << ')' << std::endl;
            return false;
        }
    }

    return true;
}

void ArrayMesh::clear_mesh()
{
    delete[] vertexByteArray;
    delete[] vertexAdjacencyList;
    delete[] vertexAdjacencyOffsets;
    delete[] allocConnOffsets;
    while( tagList )
    {
        Tag* dead = tagList;
        tagList   = tagList->next;
        delete[] dead->name;
        delete[] dead->defaultValue;
        if( dead->owned )
        {
            delete[] dead->vtxWritePtr;
            delete[] dead->eleWritePtr;
        }
        delete dead;
    }
    mDimension             = 0;
    vertexCount            = 0;
    coordArray             = 0;
    connOffsets            = 0;
    allocConnOffsets       = 0;
    fixedFlags             = 0;
    vertexByteArray        = 0;
    elementCount           = 0;
    elementType            = MIXED;
    elementTypes           = 0;
    nodesPerElement        = 0;
    oneBasedArrays         = false;
    vertexAdjacencyList    = 0;
    vertexAdjacencyOffsets = 0;
}

void ArrayMesh::set_mesh( int coords_per_vertex,
                          unsigned long num_vertices,
                          double* interleaved_vertex_coords,
                          const int* vertex_fixed_flags,
                          unsigned long num_elements,
                          EntityTopology element_type,
                          const unsigned long* element_connectivity_array,
                          bool one_based_conn_indices,
                          unsigned nodes_per_element,
                          const int* vertex_slaved_flags )
{
    clear_mesh();
    mDimension     = coords_per_vertex;
    vertexCount    = num_vertices;
    coordArray     = interleaved_vertex_coords;
    fixedFlags     = vertex_fixed_flags;
    slavedFlags    = vertex_slaved_flags;
    elementCount   = num_elements;
    connArray      = element_connectivity_array;
    elementType    = element_type;
    oneBasedArrays = one_based_conn_indices;

    if( oneBasedArrays )
    {
        coordArray -= mDimension;
        --fixedFlags;
    }

    if( nodes_per_element < 2 )
        nodesPerElement = TopologyInfo::corners( element_type );
    else
        nodesPerElement = nodes_per_element;

    vertexByteArray = new unsigned char[num_vertices + one_based_conn_indices];
    assert( valid() );
    memset( vertexByteArray, 0, num_vertices + one_based_conn_indices );
}

ArrayMesh::~ArrayMesh()
{
    clear_mesh();
}

inline const unsigned long* ArrayMesh::elem_verts( size_t e, int& n ) const
{
    assert( e < elementCount );
    if( connOffsets )
    {
        n = connOffsets[e + 1] - connOffsets[e];
        return connArray + connOffsets[e];
    }
    else
    {
        n = nodesPerElement;
        return connArray + nodesPerElement * e;
    }
}

int ArrayMesh::get_geometric_dimension( MsqError& )
{
    return mDimension;
}

void ArrayMesh::get_all_elements( std::vector< ElementHandle >& elements, MsqError& )
{
    elements.resize( elementCount );
    for( unsigned long i = 0; i < elementCount; ++i )
        elements[i] = (Mesh::ElementHandle)i;
}

void ArrayMesh::get_all_vertices( std::vector< VertexHandle >& vertices, MsqError& )
{
    vertices.resize( vertexCount );
    for( unsigned long i = 0; i < vertexCount; ++i )
        vertices[i] = ( Mesh::VertexHandle )( i + oneBasedArrays );
}

VertexIterator* ArrayMesh::vertex_iterator( MsqError& )
{
    return new IndexIterator( oneBasedArrays, vertexCount + oneBasedArrays );
}

ElementIterator* ArrayMesh::element_iterator( MsqError& )
{
    return new IndexIterator( 0, elementCount );
}

void ArrayMesh::vertices_get_fixed_flag( const VertexHandle vert_array[],
                                         std::vector< bool >& fixed_flag_array,
                                         size_t num_vtx,
                                         MsqError& )
{
    fixed_flag_array.resize( num_vtx );
    const size_t* indices = (const size_t*)vert_array;
    for( size_t i = 0; i < num_vtx; ++i )
    {
        assert( indices[i] < vertexCount );
        fixed_flag_array[i] = !!fixedFlags[indices[i]];
    }
}

void ArrayMesh::vertices_get_slaved_flag( const VertexHandle* vert_array,
                                          std::vector< bool >& slaved_flags,
                                          size_t num_vtx,
                                          MsqError& err )
{
    if( !slavedFlags )
    {
        MSQ_SETERR( err )
        ( "No data provided to ArrayMesh for Settings::SLAVE_FLAG", MsqError::INVALID_STATE );
        return;
    }

    slaved_flags.resize( num_vtx );
    const size_t* indices = (const size_t*)vert_array;
    for( size_t i = 0; i < num_vtx; ++i )
    {
        assert( indices[i] < vertexCount );
        slaved_flags[i] = !!slavedFlags[indices[i]];
    }
}

void ArrayMesh::vertices_get_coordinates( const VertexHandle vert_array[],
                                          MsqVertex* coordinates,
                                          size_t num_vtx,
                                          MsqError& err )
{
    const size_t* indices = (const size_t*)vert_array;
    if( mDimension == 3 )
        for( size_t i = 0; i < num_vtx; ++i )
        {
            assert( indices[i] < vertexCount + oneBasedArrays );
            coordinates[i].set( coordArray + 3 * indices[i] );
        }
    else if( mDimension == 2 )
        for( size_t i = 0; i < num_vtx; ++i )
        {
            assert( indices[i] < vertexCount + oneBasedArrays );
            coordinates[i].set( coordArray[2 * indices[i]], coordArray[2 * indices[i] + 1], 0.0 );
        }
    else
        MSQ_SETERR( err )( MsqError::INVALID_STATE );
}

void ArrayMesh::vertex_set_coordinates( VertexHandle vert, const Vector3D& coordinates, MsqError& err )
{
    size_t i = (size_t)vert;
    assert( i < vertexCount + oneBasedArrays );
    if( mDimension == 3 )
        coordinates.get_coordinates( coordArray + 3 * i );
    else if( mDimension == 2 )
    {
        coordArray[2 * i]     = coordinates[0];
        coordArray[2 * i + 1] = coordinates[1];
    }
    else
        MSQ_SETERR( err )( MsqError::INVALID_STATE );
}

void ArrayMesh::vertex_set_byte( VertexHandle vertex, unsigned char byte, MsqError& )
{
    assert( (size_t)vertex < vertexCount + oneBasedArrays );
    vertexByteArray[(size_t)vertex] = byte;
}

void ArrayMesh::vertices_set_byte( const VertexHandle* vert_array,
                                   const unsigned char* byte_array,
                                   size_t array_size,
                                   MsqError& )
{
    const size_t* indices = (const size_t*)vert_array;
    for( size_t i = 0; i < array_size; ++i )
    {
        assert( indices[i] < vertexCount + oneBasedArrays );
        vertexByteArray[indices[i]] = byte_array[i];
    }
}

void ArrayMesh::vertex_get_byte( VertexHandle vertex, unsigned char* byte, MsqError& )
{
    assert( (size_t)vertex < vertexCount + oneBasedArrays );
    *byte = vertexByteArray[(size_t)vertex];
}

void ArrayMesh::vertices_get_byte( const VertexHandle* vert_array,
                                   unsigned char* byte_array,
                                   size_t array_size,
                                   MsqError& )
{
    const size_t* indices = (const size_t*)vert_array;
    for( size_t i = 0; i < array_size; ++i )
    {
        assert( indices[i] < vertexCount + oneBasedArrays );
        byte_array[i] = vertexByteArray[indices[i]];
    }
}

void ArrayMesh::vertices_get_attached_elements( const VertexHandle* vertex_array,
                                                size_t num_vertex,
                                                std::vector< ElementHandle >& elements,
                                                std::vector< size_t >& offsets,
                                                MsqError& )
{
    const size_t* indices = (const size_t*)vertex_array;
    if( !vertexAdjacencyList ) build_vertex_adjacency_list();

    elements.clear();
    offsets.resize( num_vertex + 1 );
    for( size_t i = 0; i < num_vertex; ++i )
    {
        offsets[i] = elements.size();
        assert( indices[i] < vertexCount + oneBasedArrays );
        for( size_t j = vertexAdjacencyOffsets[indices[i]]; j < vertexAdjacencyOffsets[indices[i] + 1]; ++j )
            elements.push_back( (ElementHandle)vertexAdjacencyList[j] );
    }
    offsets[num_vertex] = elements.size();
}

void ArrayMesh::elements_get_attached_vertices( const ElementHandle* elem_handles,
                                                size_t num_elems,
                                                std::vector< VertexHandle >& vert_handles,
                                                std::vector< size_t >& offsets,
                                                MsqError& )
{
    const size_t* indices = (const size_t*)elem_handles;
    offsets.resize( num_elems + 1 );
    vert_handles.clear();
    for( size_t i = 0; i < num_elems; ++i )
    {
        assert( indices[i] < elementCount );
        int count;
        const unsigned long* conn = elem_verts( indices[i], count );
        size_t prev_size          = vert_handles.size();
        offsets[i]                = prev_size;
        vert_handles.resize( prev_size + count );
        std::copy( conn, conn + count, (size_t*)( &vert_handles[prev_size] ) );
    }
    offsets[num_elems] = vert_handles.size();
}

void ArrayMesh::elements_get_topologies( const ElementHandle* handles,
                                         EntityTopology* element_topologies,
                                         size_t num_elements,
                                         MsqError& )
{
    const size_t* indices = (const size_t*)handles;
    if( elementType == MIXED )
        for( size_t i = 0; i < num_elements; ++i )
        {
            assert( indices[i] < elementCount );
            element_topologies[i] = elementTypes[indices[i]];
        }
    else
        for( size_t i = 0; i < num_elements; ++i )
        {
            assert( indices[i] < elementCount );
            element_topologies[i] = elementType;
        }
}

void ArrayMesh::release_entity_handles( const EntityHandle*, size_t, MsqError& err )
{
    MSQ_SETERR( err )( MsqError::NOT_IMPLEMENTED );
}

void ArrayMesh::release() {}

void ArrayMesh::build_vertex_adjacency_list()
{
    delete[] vertexAdjacencyList;
    delete[] vertexAdjacencyOffsets;
    vertexAdjacencyOffsets = new unsigned long[vertexCount + oneBasedArrays + 1];

    // for each vertex, store the number of elements the previous
    // vertex occurs in.
    memset( vertexAdjacencyOffsets, 0, sizeof( unsigned long ) * ( vertexCount + oneBasedArrays + 1 ) );
    for( size_t i = 0; i < elementCount; ++i )
    {
        int n;
        const unsigned long* conn = elem_verts( i, n );
        for( int j = 0; j < n; ++j )
            ++vertexAdjacencyOffsets[conn[j] + 1];
    }

    // convert vertexAdjacencyOffsets from a shifted list of counts
    // to a list of offsts
    for( size_t i = 1; i <= vertexCount + oneBasedArrays; ++i )
        vertexAdjacencyOffsets[i] += vertexAdjacencyOffsets[i - 1];

    // allocate space and populate with reverse connectivity
    vertexAdjacencyList = new unsigned long[vertexAdjacencyOffsets[vertexCount + oneBasedArrays]];
    for( size_t i = 0; i < elementCount; ++i )
    {
        int n;
        const unsigned long* conn = elem_verts( i, n );
        for( int j = 0; j < n; ++j )
            vertexAdjacencyList[vertexAdjacencyOffsets[conn[j]]++] = i;
    }

    for( size_t i = vertexCount + oneBasedArrays; i > 0; --i )
        vertexAdjacencyOffsets[i] = vertexAdjacencyOffsets[i - 1];
    vertexAdjacencyOffsets[0] = 0;
}

unsigned ArrayMesh::bytes( TagType type )
{
    switch( type )
    {
        case BYTE:
        case BOOL:
            return 1;
        case INT:
            return sizeof( int );
        case DOUBLE:
            return sizeof( double );
        case HANDLE:
            return sizeof( EntityHandle );
    }
    return 0;
}

void ArrayMesh::fill( unsigned char* buffer, const unsigned char* value, size_t size, size_t count )
{
    if( !value )
    {
        memset( buffer, 0, size * count );
        return;
    }

    unsigned char* const end = buffer + size * count;
    for( unsigned char* iter = buffer; iter != end; iter += size )
        memcpy( iter, value, size );
}

ArrayMesh::Tag* ArrayMesh::allocate_tag( const char* name,
                                         bool owned,
                                         TagType type,
                                         unsigned size,
                                         const void* vertex_ro_data,
                                         void* vertex_rw_data,
                                         const void* element_ro_data,
                                         void* element_rw_data,
                                         const void* default_value,
                                         MsqError& err )
{
    // check if name is already in use
    for( Tag* iter = tagList; iter; iter = iter->next )
    {
        if( !strcmp( iter->name, name ) )
        {
            MSQ_SETERR( err )( MsqError::TAG_ALREADY_EXISTS );
            return 0;
        }
    }

    // allocate object
    Tag* result = new Tag;

    // initialize members
    result->type  = type;
    result->size  = size * bytes( type );
    result->owned = owned;
    result->name  = new char[strlen( name ) + 1];
    strcpy( result->name, name );

    result->vtxWritePtr = reinterpret_cast< unsigned char* >( vertex_rw_data );
    if( vertex_rw_data )
        result->vtxReadPtr = reinterpret_cast< unsigned char* >( vertex_rw_data );
    else
        result->vtxReadPtr = reinterpret_cast< const unsigned char* >( vertex_ro_data );

    result->eleWritePtr = reinterpret_cast< unsigned char* >( element_rw_data );
    if( element_rw_data )
        result->eleReadPtr = reinterpret_cast< unsigned char* >( element_rw_data );
    else
        result->eleReadPtr = reinterpret_cast< const unsigned char* >( element_ro_data );

    if( default_value )
    {
        result->defaultValue = new unsigned char[result->size];
        memcpy( result->defaultValue, default_value, result->size );
    }
    else
    {
        result->defaultValue = 0;
    }

    // prepend to tag list
    result->next = tagList;
    tagList      = result;

    return result;
}

TagHandle ArrayMesh::add_read_only_tag_data( const char* tag_name,
                                             TagType data_type,
                                             int vals_per_entity,
                                             const void* vertex_data,
                                             const void* element_data,
                                             const void* default_value,
                                             MsqError& err )
{
    Tag* tag = allocate_tag( tag_name, false, data_type, vals_per_entity, vertex_data, 0, element_data, 0,
                             default_value, err );
    MSQ_ERRZERO( err );
    return reinterpret_cast< TagHandle >( tag );
}

TagHandle ArrayMesh::add_writable_tag_data( const char* tag_name,
                                            TagType data_type,
                                            int vals_per_entity,
                                            void* vertex_data,
                                            void* element_data,
                                            const void* default_value,
                                            MsqError& err )
{
    Tag* tag = allocate_tag( tag_name, false, data_type, vals_per_entity, 0, vertex_data, 0, element_data,
                             default_value, err );
    MSQ_ERRZERO( err );
    return reinterpret_cast< TagHandle >( tag );
}

TagHandle ArrayMesh::tag_create( const std::string& tag_name,
                                 TagType data_type,
                                 unsigned size,
                                 const void* default_value,
                                 MsqError& err )
{
    Tag* tag = allocate_tag( tag_name.c_str(), true, data_type, size, 0, 0, 0, 0, default_value, err );
    MSQ_ERRZERO( err );
    return reinterpret_cast< TagHandle >( tag );
}

void ArrayMesh::tag_delete( TagHandle handle, MsqError& err )
{
    Tag* ptr = reinterpret_cast< Tag* >( handle );
    // find previous tag pointer in list
    if( !tagList )
    {
        MSQ_SETERR( err )( "Invalid tag handle", MsqError::TAG_NOT_FOUND );
        return;
    }
    Tag* prev = 0;
    for( prev = tagList; prev && prev->next != ptr; prev = prev->next )
        ;
    if( !prev && tagList != ptr )
    {
        MSQ_SETERR( err )( "Invalid tag handle", MsqError::TAG_NOT_FOUND );
        return;
    }
    delete[] ptr->name;
    delete[] ptr->defaultValue;
    if( ptr->owned )
    {
        delete[] ptr->vtxWritePtr;
        delete[] ptr->eleWritePtr;
    }
    if( prev )
        prev->next = ptr->next;
    else
        tagList = ptr->next;
    delete ptr;
}

TagHandle ArrayMesh::tag_get( const std::string& name, MsqError& err )
{
    for( Tag* iter = tagList; iter; iter = iter->next )
        if( name == iter->name ) return reinterpret_cast< TagHandle >( iter );
    MSQ_SETERR( err )( MsqError::TAG_NOT_FOUND );
    return 0;
}

void ArrayMesh::tag_properties( TagHandle handle, std::string& name, TagType& type, unsigned& size, MsqError& )
{
    const Tag* ptr = reinterpret_cast< const Tag* >( handle );
    name           = ptr->name;
    type           = ptr->type;
    size           = ptr->size / bytes( ptr->type );
}

void ArrayMesh::tag_set_element_data( TagHandle handle,
                                      size_t count,
                                      const ElementHandle* entities,
                                      const void* data,
                                      MsqError& err )
{
    Tag* tag = reinterpret_cast< Tag* >( handle );
    if( !tag->eleWritePtr )
    {
        if( !tag->owned )
        {
            MSQ_SETERR( err )
            ( "Attempt to set non-writeable (application owned) tag data", MsqError::TAG_ALREADY_EXISTS );
            return;
        }
        else
        {
            assert( !tag->eleReadPtr );
            tag->eleReadPtr = tag->eleWritePtr = new unsigned char[elementCount * tag->size];
            fill( tag->eleWritePtr, tag->defaultValue, tag->size, elementCount );
        }
    }
    const unsigned char* ptr = reinterpret_cast< const unsigned char* >( data );
    // as we're working with user-supplied arrays, make sure we're not
    // memcpying overlapping regions
    assert( ptr + tag->size * elementCount <= tag->eleWritePtr || tag->eleWritePtr + tag->size * elementCount <= ptr );
    for( size_t i = 0; i < count; ++i )
    {
        size_t idx = reinterpret_cast< size_t >( entities[i] );
        memcpy( tag->eleWritePtr + idx * tag->size, ptr + i * tag->size, tag->size );
    }
}

void ArrayMesh::tag_set_vertex_data( TagHandle handle,
                                     size_t count,
                                     const VertexHandle* entities,
                                     const void* data,
                                     MsqError& err )
{
    Tag* tag = reinterpret_cast< Tag* >( handle );
    if( !tag->vtxWritePtr )
    {
        if( !tag->owned )
        {
            MSQ_SETERR( err )
            ( "Attempt to set non-writeable (application owned) tag data", MsqError::TAG_ALREADY_EXISTS );
            return;
        }
        else
        {
            assert( !tag->vtxReadPtr );
            tag->vtxReadPtr = tag->vtxWritePtr = new unsigned char[vertexCount * tag->size];
            fill( tag->vtxWritePtr, tag->defaultValue, tag->size, vertexCount );
        }
    }
    const unsigned char* ptr = reinterpret_cast< const unsigned char* >( data );
    // as we're working with user-supplied arrays, make sure we're not
    // memcpying overlapping regions
    assert( ptr + tag->size * vertexCount <= tag->vtxWritePtr || tag->vtxWritePtr + tag->size * vertexCount <= ptr );
    for( size_t i = 0; i < count; ++i )
    {
        size_t idx = reinterpret_cast< size_t >( entities[i] ) - oneBasedArrays;
        memcpy( tag->vtxWritePtr + idx * tag->size, ptr + i * tag->size, tag->size );
    }
}

void ArrayMesh::tag_get_element_data( TagHandle handle,
                                      size_t count,
                                      const ElementHandle* entities,
                                      void* data,
                                      MsqError& err )
{
    unsigned char* ptr = reinterpret_cast< unsigned char* >( data );
    const Tag* tag     = reinterpret_cast< const Tag* >( handle );
    if( tag->eleReadPtr )
    {
        for( size_t i = 0; i < count; ++i )
        {
            size_t idx = reinterpret_cast< size_t >( entities[i] );
            memcpy( ptr + i * tag->size, tag->eleReadPtr + idx * tag->size, tag->size );
        }
    }
    else if( tag->defaultValue )
    {
        fill( ptr, tag->defaultValue, tag->size, count );
    }
    else
    {
        MSQ_SETERR( err )( MsqError::TAG_NOT_FOUND );
    }
}

void ArrayMesh::tag_get_vertex_data( TagHandle handle,
                                     size_t count,
                                     const VertexHandle* entities,
                                     void* data,
                                     MsqError& err )
{
    unsigned char* ptr = reinterpret_cast< unsigned char* >( data );
    const Tag* tag     = reinterpret_cast< const Tag* >( handle );
    if( tag->vtxReadPtr )
    {
        for( size_t i = 0; i < count; ++i )
        {
            size_t idx = reinterpret_cast< size_t >( entities[i] ) - oneBasedArrays;
            memcpy( ptr + i * tag->size, tag->vtxReadPtr + idx * tag->size, tag->size );
        }
    }
    else if( tag->defaultValue )
    {
        fill( ptr, tag->defaultValue, tag->size, count );
    }
    else
    {
        MSQ_SETERR( err )( MsqError::TAG_NOT_FOUND );
    }
}

}  // namespace MBMesquite